Screen size and mouse coordinates

[AggrorJorn]

I have been getting weird results with my GUI. I made a script that displays the x and y coordinate of the mouse. My window is 1024 x 768. I would expect that 768 is the bottom of the window, but the mouse coordinates indicate that height 768 is actually lower than the window. I am not sure if this is intended or a bug.

 

See the video attached:

 

The image shows a blue dot where my mouse is.

[AggrorJorn]

I made an image which display a window of resolution 1024 x 768.